The present invention is directed to a rotary pump and more particularly to a rotary vacuum pump sealed with oil or other suitable liquid with a pump system and an electric drive motor each located within a different compartment in a housing with the compartments separated by a partition and filled with oil or other liquid so that the pump system and the electric drive motor are covered with the oil.
An oil-sealed sliding vane rotary vacuum pump of this general type with a directly coupled drive motor is disclosed in German Offenlegungsschrift No. 26 20 375. The pump system and the motor are separated in the housing by a wall containing communicating apertures affording a circulation of oil. An electric signal generator is mounted on the pump shaft to monitor the speed of rotation.
In such an arrangement a shaft seal between the pump and and an externally mounted, air-cooled drive motor is avoided since such a seal is susceptible to problems. As a result, the sealing effect is considerably improved and the field of application of the pump is considerably broadened.
Nevertheless, considerable problems arise particularly with rotary vacuum pumps when the above arrangement is used in various industrial processes. The range of gaseous substances or vapor phase substances drawn off is in the range of water vapor to corrosive gases with emulsions and corrosive condensates being formed, particularly as a result of compression to over 1000 mbar at operating temperatures of about +90.degree. C. Oil contaminated in such an arrangment passes through the bearing as a result of circulation and through the communicating conduits in the partition entering into the drive motor compartment. Accordingly, the components of the drive motor as well as the electrical connections and the motor bearing are exposed to corrosive attack.
The polymerization of the condensates may even lead to jamming of the motor, because the gap between the stator and the rotor becomes clogged.
Another disadvantage is that the insulation efficiency of the oil in the motor compartment is reduced and may lead to short-circuits.
The operational reliability of the electric drive motor and, accordingly, of the entire pump arrangement is greatly impaired by these disadvantages.